<html>
<head>
<base href="http://llvm.org/bugs/" />
</head>
<body><table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - clang-cl: Implement /Gs compiler switch"
href="http://llvm.org/bugs/show_bug.cgi?id=21896">21896</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>clang-cl: Implement /Gs compiler switch
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
<tr>
<th>OS</th>
<td>Windows NT
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>Driver
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>clangbugs.10.mdwxzxkl@spamgourmet.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
</td>
</tr>
<tr>
<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>The /Gs compiler switch is ignored by clang-cl:
1>clang-cl.exe : warning : argument unused during compilation: '/Gs0x7fffffff'
1>...
1>main.obj : error LNK2019: unresolved external symbol __chkstk referenced in
function "int __cdecl mainCRTStartup(void)" (?mainCRTStartup@@YAHXZ)
The /Gs compiler switch is needed to suppress calls to __chkstk (the stack
probing function used by MSVC), e.g. when one carefully uses stack memory so
that all necessary stack probes are initiated, or when compiling with
/NODEFAULTLIB (as __chkstk would then be undefined).
One workaround could be to forward /Gs0x7fffffff or /Gs2147483647 (the maximum
value for /Gs, which is the recommended way to suppress all __chkstk() calls)
to -mno-stack-arg-probe. Currently a /Gs value of 4096 seems to be hardcoded in
LLVM:
<a href="http://llvm.org/klaus/llvm/blob/master/lib/Target/X86/X86FrameLowering.cpp#L-709">http://llvm.org/klaus/llvm/blob/master/lib/Target/X86/X86FrameLowering.cpp#L-709</a>
Specifying -mno-stack-arg-probe will probably set UseStackProbe to false.
Reference:
<a href="http://msdn.microsoft.com/en-us/library/9598wk25">http://msdn.microsoft.com/en-us/library/9598wk25</a></pre>
</div>
</p>
<hr>
<span>You are receiving this mail because:</span>
<ul>
<li>You are on the CC list for the bug.</li>
</ul>
</body>
</html>